Method for the production of sodium penicillin



Patented July 20, 1954 METHOD FOR. THE PRODUCTION or SODIUM PENICILLINJacques L. Wachtel, Lawrenceburg, Ind., Donald It. Croley, Cincinnati,Ohio, and Justin J. Murtaugh, Guilford, Ind., assignors to SchenleyIndustries, Inc., a corporation of Delaware No Drawing. ApplicationOctober 23, 1948,

Serial No. 56,253

1 Claim. 1

This invention relates to a new and useful method for the preparation ofpenicillin, and more particularly to a method for the preparation of thepure sodium salts of penicillin from organic base salts of penicillin.

It is an object of this invention to produce colorless, pure,crystalline sodium salts of penicillin from impure penicillin-containingpreparations. It is a, further object of the invention to obtain sodiumsalts of penicillin having a higher benzyl penicillin (penicillin G)content than the impure penicillin-containing preparations.

Heretofore, penicillin has generally been separated from fermentationbroths and aqueous solutions by adsorption onto and elution fromactivated carbon and/or by solvent extraction processes, using solventssuch as chloroform, ether, amyl acetate, butyl acetate and the like,under acid conditions. Solutions of the desired alkali or alkaline-earthsalts of penicillin where formed from these solvent solutions bycontacting them with aqueous solutions or suspensions of alkali oralkaline-earth hydroxides, carbonates, or bicarbonates; the resultingaqueous phase could be separated and dried to yield solids consisting ofnon-crystalline penicillin salts and impurities. Usually such driedpreparations were yellow or orange in color, and had a potency of 500 to1000 units per milligram, which usually indicated the presence of 40% to70% impurities, since pure sodium benzyl penicillin (penicillin G) has apotency of 1667 units per milligram. The desirability of producingpenicillin preparations of greater purity and less color has beengenerally recognized, but processing methods heretofore r can beproduced in good yield by reacting organic base salts of penicillin withselected sodium salts under certain conditions, as hereinafterdescribed.

The formation of organic base salts of penicillin is known. Thus, forexample, the triethylammonium salt, the N-ethyl piperidine salt, or thecyclohexylamine salt have been formed by re acting ether or amyl acetatesolutions of penicillin with triethylamine, N-ethyl piperidine, orcyclohexylamine, respectively. In contrast to most of the non-penicillinsubstances, these organic base salts of penicillin are sparingly solublein their reaction mixtures and therefore afford a means for the partialseparation of penicillin from most of the impurities present. However,the separation from impurities is not complete, and the organic basesalts are usually yellow, due to impurities. Furthermore, these organicbase salts are not acceptable forms for the therapeutic administrationof penicillin, and heretofore it has not been known to convert, otherthan by solvent extraction methods, such organic base salts to thesodium salts of penicillin which are acceptable therapeutic forms.

It has been found according to this invention, that organic base saltsof penicillin can, under certain conditions, be reacted directly withsodium salts of organic acids to yield sodium salts of penicillin of anextraordinary high degree of purity. The process of this inventioninvolves a so-called double decomposition reaction in an organic solventsolution, which reaction may be represented by the following equation:

B Pen NaA NaPen B A Organic base Reagent Sodium Organic base salt ofpenisodium penicillin s cillin salt (product) (by-product)(precipitated) (soluble) The reactants are dissolved in organic solventswhich are selected for their ability to dissolve their respectivesolutes and, upon intermixing in the reacttion mass, to form a singlephase liquid mixture in which the desired product of the reaction, thesodium salt of penicillin, is substantially insoluble, and in which theother components of the reaction system remain in solution.

Organic base salts of penicillin, such as the triethylammonium salt, theN-ethyl piperidine salt, the cyclohexylamine salt, the N-ethylmorpholine salt, the N-methylmorpholine salt, theN-ethyl-alpha-pipecoline salt, the N-ethyl-hexahydro-2,6-lutidine salt,the benzylamine salt, or the di-isopropylamine salt, exemplify organicbase salts which may be used as a starting material for our process. Theinvention is not limited to the use of these organic base salts.

Reagent sodium salts or compositions which may be used in this inventionare, for example: sodium thiocyanate, sodium chlorate, sodiumperchlorate, the various sodium phenolates, sodium iodide, sodium ethylisonitrosocyanoacetate and its homologues, sodiumdimethyl-dithiocarbamate and the various sodium dialkyldithiocarbamates.The invention is not limited to the use of these salts.

As some examples of the sodium phenolates, also designated as sodiumphenates and. sodium phenoxides, reference is made to the following:sodium phenoxide, o-methyl sodium phenoxide, sodium cresylate, sodiump-tert-amyl phenoxide, and the sodium salt of o-hydroxy acetophenone.

As some examples of the sodium dialkyldithiocarbamates, reference ismade to the following: sodium dimethyldithiocarbamate, sodiumdiethyldithiocarbamate, and sodium dibutyldithiocarbamate.

The following are examples of suitable solvents for the organic basesalts of penicillin in this process, without limiting the inventionthereto: (a) chlorinated organic liquids, such as methylene dichloride,chloroform, sym-tetrachloroethane, and benzal chloride; (1)) ketones,such as acetone, methylethylketone, diethylketone, andmethylpropylketone; and lower monohydroxy aliphatic alcohols, having 1-5carbon atoms, such as methanol, ethanol, propanol, isopropanol,n-butanol, sec-butyl alcohol, and the several amyl alcohols. Chlorinatedliquids having two substituent chlorine atoms and at least onesubstituent hydrogen atom on the same carbon atom are especially suitedfor serving as solvents for the organic base salts of penicillin and asthe principal liquid constituent of the reaction mass. This desirablestructure is represented by the configuration where Z representshydrogen, chlorine, or another carbon atom or an organic radical whichmay or may not contain additional chlorine atoms. This action isattributed to hydrogenbonding between the solvent and the organic basesalt of penicillin, but the method of the present invention is not inany way limited or restricted by this explanation.

As examples of suitable solvents for the reagent sodium salts in themethod of the invention, the following are cited, without limiting theinvention thereto: (a) lower aliphatic alcohols, preferably having, 1-5carbon atoms, such as ethanol, ethylene glycol, allyl alcohol,n-propanol, isopropanol, n-butanol, isobutyl alcohol, the amyl alcohois,(b) ketones, such as acetone, methyl ethyl ketone, diethyl ketone,methyl isobutyl ketone, and (c) nitriles, such as acetonitrile,propionitrile, and butyronitrile. These solvents may be used without theaddition of water, although sometimes it is desirable to add a smallquantity of water, say up to by volume, in order to increase thesolubility of the reagent sodium salt in the organic liquid. Also, ithas been found that the addition of such a small quantity of water tothe organic liquid usually helps to retain colored impurities in themother liquor of the reaction mass, resulting in a whiter precipitatedsodium penicillin salt.

The above-named classes of solvents meet the specified. requirements forthe solvents to be used in the method of this invention.

The reaction above described may be conducted over a wide temperaturerange, say between 10 C. and +40 C. However, there are practicaladvantages in working at approximately room temperatures, say from C. to0., because at these temperatures the organic base salt and the reagentsodium salt are soluble to a convenient extent in their respectivesolvents, and the end-products, namely, the sodium penicillin, is notexcessively soluble in the reaction mixture.

The precipitation reaction upon which this method is based operates overa wide range of concentrations of organic base salts of penicillin andreagent sodium salts in their respective solvents. However, it isusually preferred to use a substantially saturated solution of organicbase salt in the selected solvent, so as to minimize the loss of productdue to its solubilty. Concentrations of from 200 to 4.00 grams oforganic base salts of penicillin per liter of chlorinated solvent havebeen found especially desirable in this method.

The reagent sodium salt solution may also be employed. over a fairlywide range of concentrations. Usually it is preferred to use asubstantially saturated solution of the reagent sodium salt in theselected solvent, so as to keep the volume of the reagent solution lowand so as to minimize loss of the reaction product due to solubility inthe liquids employed. Either anhydrous solvents or solvents containingup to 10% of water by volume may be used in this proceess. Reagentsodium salt solutions of concentrations varying from 10 to 300 grams perliter of solvent give the desired results in this process. Since some ofthe sodium salts which are used as re agent salts possess limitedsolubilities in some of the solvents named, it is often, but not always,advantageous to increase this solubility by adding a small amount ofwater to the solvent employed. Very often the water of crystallizationin the reagent sodium salt is sufficient to bring the solubilitieswithin workable limits. The amount of water present must be limited, aswill be apparent to those skilled in the art, because too much Water inthe reaction mixture will interfere with the precipitation of theproduct sodium salt. It is necessary to adjust the Water content so asto secure the best over-all results in the process from the standpointsof yield, color, and benzyl penicillin content of the product sodiumsalt.

The organic base salt of penicillin which is used as the startingmaterial for the process need not have any stipulated degree of purity.All preparations which have been tested have been found suitable for thereactions of this method.

Substantially stoichiometric proportions of reactants are used in thedescribed reaction, although sometimes it is preferred to use an excessof one of the reagents, in accordance with usual practice in conductingreactions in organic chemistry.

When the specified reagent sodium salts are reacted with organic basesalts of penicillin under the described conditions, precipitation ofsodium penicillin occurs. The precipitated sodium penicillin may beseparated from the reaction mass by filtration, centrifugation, or othersuitable means.

. When the crystals of sodium pencillin are separated from the reactionmass, it is usually desirable to wash the crystals so as to removeadhering impurities. The solvent mixture employed in the reaction, thereagent solvent, or acetone, used in small quantities, are suitablewashing liquids. It is usually preferred to wash the crystals first withthe reagent solvent in order to remove excess reagent salt which mightbe present. It is then usually preferred to wash with acetone, toexpedite drying of the endproduct.

In addition toproviding a means of obtaining high yields of pure,therapeutically acceptable penicillin from impure preparations, themethod of this invention results in a preferential precipitation of thesodium salts of benzyl penicillin from the reaction mixture, which is animportant advantage because benzyl penicillin is now the commerciallydesired form of penicillin. The

concentration of benzyl penicillin which may be obtained in the sodiumpenicillin product is a function of the benzyl penicillin content of theorganic base salt used as starting material for the process. Thus, bythis process, an organic base salt of penicillin consisting of about 50%benzyl penicillin yields sodium salts of penicillin which contain about80% of benzyl penicillin, whereas organic base salts which contain from75 to 85% benzyl penicillin yield, by the method of this invention,sodium salts of penicillin containing in excess of Sill-95% benzylpenicillin, as measured by accepted methods of analysis for benzylpenicillin, such as the ultra-violet spectrophotometer method, or theN-ethyl piperidine precipitation method.

As typical of the manner in which this invention may be practiced, thefollowing examples are given, although these examples are to be considered in no way restrictive.

Example 1 5 gm. of yellow triethylarnmonium penicillin containing 90%benzyl penicillin (as determined by the N-ethyl piperidine method) weredissolved in 13 ml. of U. S. P. chloroform. To this solution then added,with stirring, a solution of 5 gm. of sodium iodide in 40 ml. ofacetonitrile. Crystals of sodium penicillin separated within a fewseconds, and after cooling the mixture for minutes in an ice bath, theprecipitate was filtered on" by suction and washed with a littleacetonitrile, followed by washing with a little acetone. The productweighed 4.032 gm., was white in color, assayed 1660 units/mg.(penicillinase assay) and contained 93% benzyl penicillin (BL-ethylpiperidine method). The recovery of bensyl penicillin was quantitative;the recovery of total penicillins amounted to 98.4%.

Example 2 in an ice bath for a half hour and the precipi- 0 tate wasthen filtered oil and washed with a little acetone. The very pale yellowproduct weighed 3.824 gm., contained 95% benzyl penicillin (N-ethylpiperidine method) and assayed 1658 units/mg. (penicillinase assay). Therecovery of benzyl penicillin amounted to 98.5%; the recovery of allpenicillins was 93.5%.

Example 3 gm. of yellow triethylammonium pencillin (98% benzylpenicillin as determined by the N- ethyl piperidine method) weredissolved in 60 ml. of tetrachloroethane. To this solution was added,with stirring, a solution of 15 gm. of sodium phenolate (CeHeONa-) in 30ml. of acetone. Sodium penicillin started to precipitate almostimmediately. The mixture was placed in an ice bath for a half hour. Thecrystals were then filtered off by suction and washed with acetone. l'hepale yellow dried product weighed 16.624 gm. The recovery of penicillinG and of total penicillins was practically quantitative.

Example 4 3 grams of yellow triethylammonium penicillin (containing83.4% of benzyl penicillin as determined by the ultravioletspectrophotometric method) were dissolved in 12 ml. ofsym-tetrachloroethane and to this solution was added with stirring, asolution of 1.55 gm. of sodium dimethyldithiccarbamate (CH3) 2NCSSNa2H2O) dissolved in 32 ml. of n-butanol. Crystals of sodium penicillinseparated within a minute. The mixture was then cooled an ice bath for ahalf hour, and the precipitate was filtered off by suction and washedsuccessively with a little tetrachloroethane, n-butanol and acetone. Thedried product (1&2 gm.) was white, assayed i660 u.,/mg. (penicillinasemethod) and contained 98% benzyl penicillin (ultravioletspectrophotometer method). The recovery of benzyl penicillin amounted to92%; the recovery of all penioillins was 78%.

Preferred embodiments of this invention have been described, butnumerous changes, omissions, additions and variations can be madewithout departing from its scope.

We claim:

Process for the formation of sodium penicillin which comprisesmetathetically reacting a tertiary amine salt of penicillin and sodiumperchlorate in a polar organic solvent solution.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,459,315 Goldberg et a1. Jan. 18, 1949 2,463,943 Behrens 8,1949 2,493,625 Goldberg et a1. Jan. 3, 1950 FOREIGN PATENTS NumberCountry Date 607,004 Great Britain Aug. 24., 1948 OTHER REFERENCESAbraham et al.: The British Journal of Exptl Pathology, vol. 23, June1042, page 113.

British Report, CMR-Br-234 (PB-79927), December 5, 1947 (received N. Y.,April 18, 1946), page 4.

